I like the idea behind the game representing sea level rise, but in practice I do think it has tilted the scales too much towards inland cities. I think districts need to get adjacencies towards being built on coastal tiles. It could represent them being more accessible, more appealing, something like that. Maybe gold yields being increased for coastal tiles, or harbors being reduced in cost for coastal cities. Though in that case England and Phoenicia's unique harbors would need to be buffed a bit to compensate for them not getting as much benefit out of the half-cost perk for unique districts. I do think aqueducts should be an improvement in the next iteration, or have their range increased somehow. It could help coastal cities quite a bit. They definitely seem to be moving towards improving coastal cities with the maritime city states like MaryKB mentioned.